In today's web-based application hosting environment, a single portal may allow connection to many externally hosted and independently operated web-based heterogeneous applications that require user authentication. It would be most useful to provide single sign-on (SSO) to these applications. However, there are a number of challenges to overcome in providing SSO functionality. These challenges include, providing SSO transparency to the end user and providing portal and application security while limiting the need to modify client software and conserve portal bandwidth usage.